Connected: An Internet Encyclopedia
RFC 1945 - 10.12 Pragma

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### 10.12 Pragma

The Pragma general-header field is used to include implementation- specific directives that may apply to any recipient along the request/response chain. All pragma directives specify optional behavior from the viewpoint of the protocol; however, some systems may require that behavior be consistent with the directives.

           Pragma           = "Pragma" ":" 1#pragma-directive

           pragma-directive = "no-cache" | extension-pragma
           extension-pragma = token [ "=" word ]

When the "no-cache" directive is present in a request message, an application should forward the request toward the origin server even if it has a cached copy of what is being requested. This allows a client to insist upon receiving an authoritative response to its request. It also allows a client to refresh a cached copy which is known to be corrupted or stale.

Pragma directives must be passed through by a proxy or gateway application, regardless of their significance to that application, since the directives may be applicable to all recipients along the request/response chain. It is not possible to specify a pragma for a specific recipient; however, any pragma directive not relevant to a recipient should be ignored by that recipient.

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Connected: An Internet Encyclopedia
RFC 1945 - 10.12 Pragma